Now, however, a first-of-its-kind study has taken a broader look at the spread of fake news on social media, and the results are incredibly troubling.

In February, the US Justice Department charged 13 Russians with allegedly trying to "promote discord in the United States" by posing as Americans on social media. "Deceptive bots create the impression that there is a grassroots, positive, sustained human support for a certain candidate, cause, policy or idea", the New Democrat Network said. They also found it took true stories about six times longer to reach 1,500 people than false stories.

The researchers examined thousands of stories disseminated on Twitter and trillions of tweets between the years 2006 and 2017.

By nearly all metrics, false cascades outpaced true ones. The definition of what the researchers defined as news is broader than the traditional meaning, and they accepted any asserted claims made on Twitter as news.

Political news was the largest rumour category with about 45,000 "cascades".

The amount of false news on Twitter is clearly increasing and spikes during key events, like the USA presidential elections of 2012 and 2016.

The researchers selected stories that had been investigated by six fact checking sites including snopes.com and politifact.com. Similarly, the researchers identified common themes in the phrasing of replies to false rumors - users more frequently expressed words associated with disgust and surprise when they commented on untruths.

While true news stories nearly never got retweeted to 1,000 people, the top 1 percent of the false ones got to as many as 100,000 people.

Recently, social media companies have been made to face USA and United Kingdom lawmakers about the role of bots on their platforms.

"I don't think it's because of Twitter and other social media platforms, but because of something that has always existed in human nature" Vosoughi said.

It's real people - not bots - who are mainly responsible for passing on fake information, Aral says. By conducting the research this way, the group was able to determine what was extremely likely to be fake news rather than an article that was only debunked by one or two websites.

Not all bots are malicious, for example, publishers use bots to automatically tweet news headlines.

Lead author Soroush Vosoughi, an MIT data scientist, said the three false stories that traveled the farthest and fastest were about a Muslim guard called a hero in the Paris bombings of 2015; an Iraq war veteran finishing as runner-up to Caitlyn Jenner for an ESPN courage award; and an episode of "The Simpsons" that had a story line in 2000 about a Trump presidency.

"I was somewhat surprised to see bots didn't play a starring role", Roy said. A recent study of the browsing histories of thousands of USA adults in the months before the 2016 election found that false news accounted for only a small portion of the total news people consumed.

Is it actually changing people's minds? Twitter earlier this month said it is seeking help from outside experts to better deal with the problem.

"We are not going to remove content based on the fact this is untrue", he told British MPs in February.

"When you're unconstrained by reality, when you're just making stuff up, it's a lot easier to be novel", said Sinan Aral, one of the study's co-authors.

"Now behavioural interventions become even more important in our fight to stop the spread of false news", Aral says.

That's because people can gain attention on social media by sharing new information, regardless of its accuracy, Aral said.

Bot panic or not, Dr Vosoughi said social media companies may need to intervene.